Frequently asked questions
Adelaide's coastline is one connected system but some of our beaches are experiencing significant erosion.
- The problem
- The current science
- What are the next steps?
- What is the current state of our metropolitan beaches?
- What happens if nothing is done to address erosion at West Beach?
Some parts of the Adelaide beaches are experiencing significant sand loss and erosion of the sand dune system.
The sand along Adelaide’s coast naturally moves northward, by the wind and waves. This causes sand to build up on our northern beaches such as Semaphore, and causes sand loss and erosion along our southern and central coast such as West Beach and Henley Beach South.
The State Government manages the metropolitan coastline to enable the community to enjoy sandy beaches. Works to move sand has occurred across the metropolitan beach system for nearly 50 years.
Sand is a finite resource - it needs to be shared equitably along our coastline so we can all enjoy Adelaide's stunning coastline.
- West Beach has had serious and ongoing erosion for several years. Beach levels at West Beach and Henley Beach South have been at their lowest in recent years than at any other time since records began.
- From Henley Beach to the north, the beaches are generally in good condition as the sand lost from southern beaches drifts north.
- Sand continues to accumulate in Largs Bay, with wide dunes from around the Semaphore jetty northwards.
- The beaches in the southern part of the coast (from Glenelg to Kingston Park) are generally stable because of successful beach management. The pipeline from Glenelg to Kingston Park currently pumps approximately 100,000 cubic metres (m3) of sand successfully each year.
What happens if nothing is done to address erosion at West Beach?
If sand isn’t replenished at West Beach, the erosion problem will get worse and progressively move northward. This means that beaches at Henley Beach South, Henley Beach and Grange will erode. Coastal infrastructure, roads, facilities and beach amenity would then be subject to severe damage from storm surges.
Further north, the dunes at Semaphore, Largs Bay and North Haven will continue to grow bigger. Sand will continue to build up on these beaches, with the water becoming very shallow to swim or fish in, and it is likely that the jetties will eventually become land locked.
In 2017, a coastal processes modelling study was commissioned by the Department for Environment and Water, the Coast Protection Board, the City of Charles Sturt and West Beach Parks to better understand the coastal processes at West Beach and to examine alternative management options. This was needed because of the ongoing loss of sand each year at West Beach.
External consultants and international coastal experts DHI completed a report in 2018.
- The research undertaken by DHI has shown that the sand loss at West Beach (the section of coastline running north from the West Beach boat harbor at West Beach Parks to the Torrens Outlet) is significant, and greater than previously estimated.
- The report made it clear that even if current management activities were maintained, erosion will continue around West Beach and Henley Beach South, and progressively move north.
- The report tested out three alternative scenarios for managing the beach and dune erosion at West Beach, with their results modelled. All three options involve beach replenishment, and varied by bringing in differing amounts of sand over different timescales.
During the course of the study, the scope was amended to expand the analysis of beach profiles along the entire system from Kingston Park to Largs Bay, to enable a better understanding of the influence of management of adjacent beaches on West Beach and vice versa. This expanded analysis also provides insight into the management of the entire Adelaide beach system.
What are the next steps?
- In April 2022 the South Australian Government announced that construction of a sand recycling pipeline between West Beach and Semaphore South will be halted.
- Instead a comprehensive review of all options available will be undertaken to ensure a long-term solution is found which puts community and the environment at the core.
- Externally sourced sand will continue to be brought into West Beach from quarries and the Semaphore South breakwater while the review is completed.
- More information on the review and community engagement will be provided when available.
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Why aren't structures like groynes built to try to reduce the natural drift of sand northward? What other alternatives have been looked at?
Structures of the size required to have an impact are very expensive to construct. These areas would then require large volumes of sand to be brought in from an external source to “pre-fill” them. This pre-filling with external sand is essential otherwise the coast to the north of each structure would be eroded.
In addition, the experience with structures on the Adelaide coast and elsewhere in South Australia is they also trap large quantities of beach-cast seagrass, which has an impact on the usability of the beaches and increases management costs.
When factoring in these aspects, the sustainable approach to managing our beaches involves recycling sand from areas where sand builds up to areas of loss. This means the protection of Adelaide’s beaches can be achieved without negative impacts from structures, which would tend to interrupt our long sandy beaches.
Options involving the construction of hard engineering structures to re-orientate the West Beach shoreline were considered by DHI and included offshore breakwaters and headland control structures. A range of risks and disadvantages were identified with these options: they are costly to install, require large quantities of sand, trap seagrass wrack, can be a safety hazard, are visually unappealing, interrupt recreational beach use and can cause the coast on the northern side of the structure to become starved of sand.
Why is sand under the surface of the beach grey or black in colour?
The sand collected from Adelaide’s beaches is sometimes coloured grey to black because of the naturally decomposing seagrass content. This is particularly noticeable if you dig below the surface of the beach in areas where seagrass wrack accumulates. This quickly dries and turns white/yellow after being exposed to the sun, wind and rain.
During the 1980s and 1990s, the Seacliff and Brighton coast was suffering from severe erosion that threatened the foreshore. To address this, a large scale beach replenishment with sand sourced externally was undertaken.
During the 1990s over 1 million cubic metres of sand was dredged from sand deposits offshore of Port Stanvac and delivered to that section of the coast, which formed and stabilised the dunes and in turn helped to stabilise the beach.
The operation of the sand recycling pipeline from 2013 onwards has maintained sand volumes and further stabilised this part of the coast and will continue to do so as required.
Local councils play a critical role in protecting regional assets from coastal hazards and maintaining coastal areas for all South Australians and tourists.
Grants are available to repair, restore and sustain regional coasts in partnership with local councils. The program is open to councils with a particular focus on the outer metropolitan and regional areas. Learn more.